A method of a user who uses a smartphone in an existing country to perform a telephone and data communication using the smartphone after going to a foreign country basically includes two methods.
If roaming, that is, the first method, is used, the user can use a telephone and data service as in the existing country even in the local country by requesting roaming at the airport without separately replacing a universal subscriber identification module (USIM) card. Furthermore, recently, most of smartphones have been configured to automatically perform roaming when a user powers off the smartphone and then powers on it after departure for user convenience.
If a method of mounting a local USIM, that is, the second method, is used, the user can freely use the smartphone in the local country within a preset amount of money as if the user uses a prepaid phone. In order to use this method, the user has to purchase a local USIM in the local country, mount the local USIM on the smartphone, and use the smartphone within the range in which the amount of money set in each USIM is not exceeded.
As described above, a method of using a smartphone in a local (foreign) country without any change is already present. If the methods are used, a relatively high cost must be paid compared to a cost for using a smartphone in an existing country.
First, roaming has a problem in that a cost for the roaming is six times higher than a cost for a prepaid phone in average to the extent that an excessively high roaming charge is introduced according to many news that are recently reported. Furthermore, if a user makes a call to an acquaintance who lives in a local country in the state in which the user uses roaming, the call is treated as an international call and thus a charge higher than a common call charge is assigned to the corresponding call.
Furthermore, in the case of the method using a local USIM, the local USIM can be used for a predetermined period only and cannot be used in other periods. Accordingly, if a user does not fully use the amount of money charged in the local USIM, the amount of money results in a profit of a local communication company, and the user cannot get the remaining amount back in any form.
A user has to inconveniently find out the place where a charging machine is located or a Wi-Fi zone if the amount of data charged by the user is fully consumed while using a prepaid phone. If the user is not proficient in a corresponding local language, the user may experience inconvenience attributable to the language barrier in the process of finding out a charging machine and charging the amount of money used through the charging machine.